3W100
 

I have a 3W100 from AI and have 62 Flights on engine and noticed that I have some play on the crank. You can take the crank and slide it in and out, End PLay. Is there a spec. on this or should there be no movement. I have not checked the amount of play let but seems to be alot.

RE: 3W100
 

End play is required for the engine to live. How much is another query?

Contact Cactus Aviation or Aircraft International for the accepted numbers for your engine.

RE: 3W100
 

Quick rule of thumb. If you can MOVE the crankshaft, especially fore-aft, there is a PROBLEM. The 3W uses ball bearings, which are sealed, and they are pressed onto the crankshaft. If you can mofe the crankshaft fore-aft, that means the shaft is either sliding on the inner race of the bearing (which it's NOT supposed to do. .press fit) or that the bearings are starting to go bad, allowingyou to move things around.

Things usually loosen up just a little bit when the engine is hot, and I've seen BME's that you could move the front of the crankshaft on, because of the bearing design. But, no 3W I have ever seen allows the crank to move in a noticeable way. The bearings are massive, beefy things on that motor, a true exercise in overkill, so there should be little if any perceptible play in the crankshat.

Best bet is to contact your supplier and ship it in for a good going over.

RE: 3W100
 

some designs DO require fore aft clearance -
This is done to prevent end loading the bearings.
The cases expand and unless the crank can move in one bearing - an end load will occur.
most engines once fully assembled, will have no detectable "end play"
However - one of the bearings is taking the end load - the other is not.
When specifying bearing-- the load ratings call out rpm-side (end) load and possible radial loads .
The worst setup is when the side (end) loads change with case expansion.
Typically- When I redo an engine to run fast -- I setup the crank to bearing clearances such that case growth never end loads the bearings .
Now - back to sleep -

RE: 3W100
 

I never took apart the lower end of my 3W-100s, but Kris is correct. There is no detectable axial or radial play in the crankshaft when gripping the prop - hot or cold. I've also got over 600 flights on one and about 200 flights on the other. While we're talking about bearings, there should also be no detectable play in the rod needle bearings when you pull the piston straight up and down.

RE: 3W100
 

well thanks for the info, I will call 3w and see what they say.

RE: 3W100
 

Dick, it depends on WHICH bearing is holding that crankshaft from moving forward. It DOES have to be held from moving around, right? the front, or #1 bearing, in most of these engines, is the one with the tightest fit on the crank, and takes the majority of axial and linear loads, so it should never become "loose" or have the crankshaft moving fore-aft in any great way.

One thing to remember, as well, 3W sets their engines up pretty well, and I'm sure the bearings are installed with the consideration for about .001" or so of fore-aft crankcase growth as the engine heats up. Plus, 3W uses sealed bearings not ones with loose races that allow the crankshaft to effectively "float" on them.

One thing I learned a LONG time ago, with ball bearings, it does not matter how much "float" you have in a static non-running environment, what matters is how true and drag-free the bearing runs under load. Too much "float" can actually cost you power and cause premature wear. If 3W designed their engines a certain wayu, deviating from taht would probably not be the best idea. In this case. . the crank is moving. 3W did NOT design it that way.

Think I'll stay awake for a while. You should try the same :)